Sciencemadness Discussion Board

Anyone ever built an overhead stirrer?

Hilski - 29-10-2006 at 10:42

I'm going to try and build an overhead stirrer similar to the one shown here:

http://designer-drugs.com/pte/12.162.180.114/dcd/chemistry/e...

I mostly want to use it for my manganese ammonium alum oxidation of toluene (and other stuff) experiment which really needs overhead stirring.

https://sciencemadness.org/talk/viewthread.php?tid=6882

As you can see the difference is that my reaction is carried out in a large glass jar with an open top. I have to use a glass rod, because of the heated 60% H2SO4, so I will have to attach it to the stainless shaft of the original beater that came with the mixer. I have to find a way to stabilize everthing since I wont be using a rubber stopper with a glass tube, as is shown in the link I posted obove. I have a few ideas that will probably work, I just wanted to hear some ideas from some of the folks here before I decided anything.

Thanks

-Hilski

Magpie - 29-10-2006 at 20:34

What you are saying I think is that you need to provide a bearing to prevent horizontal movement of your glass shaft.

It seems like a small block of Teflon, drilled slightly oversized for the shaft would do it. The block could be held in position with a ringstand and clamp or such.

not_important - 29-10-2006 at 22:02

Teflon is overkill, if it's not going to get heated much then high density or UHMW polyethylene would work well for less than 1/6 the cost of teflon. And it should be easier to find, as well.

Use as long as of shaft as is practical, and put some vapour barriers between the motor and the solution. A sheet of thick polyethylene as a loose cover for the beaker, and another on the underside of the motor might do.

When working with corrosive solutions, it wasn't uncommon to place the motor some distance away and use a flexible shaft or belt-and-pulley rig to transmit power to the stirrer shaft. that's most likely more work than you want to do but might be worth thinking about for a few seconds.

evil_lurker - 29-10-2006 at 22:55

http://www.eastwoodco.com/shopping/product/detailmain.jsp?it...

That right there with the drill mount would be the shiznit.

The shaft is only a measly $20.

[Edited on 30-10-2006 by evil_lurker]

Hilski - 30-10-2006 at 11:38

Yes. Basically I need to make a bearing for the stirrer shaft, to keep it from moving around too much. If I could come up with a good way to make a rigid connection between the steel shaft and the glass rod, a bearing probably would be uneccessary in this case. But since I will be using a flexible connection (Probably a piece of hose) I am going to need it.

UHMW block (bearing) mounted onto a piece of Lexan (beaker cover) was what I was thinking, and was really the only viable thing I could even come up with. I especially like it since UHMW in all kinds of shapes and sizes is already freely available to me :D. The long flexible shaft idea is a good one. I may try a small diameter piece of fuel or hydraulic hose for this. It would still have to be relatively straight above the vessel, but the motor could be mounted pretty high above it I guess.

If I could find some small diameter nickle rod locally, I would use that. Then I could just weld the nickle rod to the shaft on the mixer and be done with it. Come to think of it, there may be some 1/8" or 5/32" nickle welding rods around here somewhere if I can find them.

Anyhow, once I get this contraption built, I'll post some pictures of it in this thread.

Thanks for the replies.

-Hilski

bio2 - 30-10-2006 at 17:03

A motor from an old printer in a standard clamp on a ringstand
is more versatile and smooth running.

One of these easily stirs 12 liter of sludge/muck or whatever yet slows down to only about a hundred RPM

Use the carriage motor with an LM317K (TO3 package) connected as constant current regulaor

Hilski - 31-10-2006 at 07:35

Quote:
Originally posted by bio2
A motor from an old printer in a standard clamp on a ringstand
is more versatile and smooth running.

One of these easily stirs 12 liter of sludge/muck or whatever yet slows down to only about a hundred RPM

Use the carriage motor with an LM317K (TO3 package) connected as constant current regulaor


Thanks for that idea. I would have never thought of using a motor from a printer carriage. I'm definately going to look into this one, as I have a couple of old printers lying about. Is this something you have tried before?

Thanks again.

Hilski - 31-10-2006 at 09:35

I just took apart an old printer I had. These are the motors that were in it. Are they suitable for the setup you were talking about?




Now I just need to figure out a good way to couple the glass stir rod to the motor. Thanks again for the idea.

[Edited on 31-10-2006 by Hilski]

Magpie - 31-10-2006 at 09:55

What about a "chuck" of some kind, like on a drill. Perhaps rubber lined. :D

Hilski - 31-10-2006 at 10:03

Quote:
Originally posted by Magpie
What about a "chuck" of some kind, like on a drill. Perhaps rubber lined. :D


That would be ideal.
I was thinking of machining an aluminum coupling with a set screw to hold the rod, but the screw may crush the glass.

[Edited on 31-10-2006 by Hilski]

evil_lurker - 31-10-2006 at 10:45

Ya know, kantu200 ebay store has some good deals on overhead stirrer paddles.

You should be able to get a rather large PTFE stirrer with stainless center for less than $40.

Magpie - 31-10-2006 at 16:22

Your earlier idea has merits. E.g., fix a short metal stub shaft of the same diameter as your glass shaft to the motor shaft end. Then get a short piece of vacuum hose with ID such that it provides an interference fit to the glass shaft and the motor stub shaft. The PE (or even Nylon?) bearing(s) will assure glass shaft alignment to the stirred vessel.

This connection has the advantage of being cheap, easy, and will tolerate some misalignment of the glass and motor shafts.

There are other flexible couplings available on the market. But the above is likely the cheapest and best. The only disadvantage I can see is that it might have less tolerance to high torque than other types of couplings. But with glass you are going to be limited to low torque anyway.

Hilski - 1-11-2006 at 09:23

Now I know why I never considered using printer motors. They're ALL bipolar stepper motors, and I don't feel like building a stepper motor controller. I don't know why in god's name I didn't notice that when I took them out of the printer.

I guess I'll just use the kitchen mixer for the time being until I get a more suitable (read: no programming or soldering ICB's because I'm lazy) motor. Unless of course, I can find one in the scrap pile of electronic junk that I've built in the past.

bio2 - 1-11-2006 at 10:45

....They're ALL bipolar stepper motors......

Not in the ones I took apart. There are 3 motors two are small steppers and the larger round one that moves the carriage belt is 18V PM type that will run down below 4v and still produce a lot of torque. It's the one with only two leads.

I have two of these from HP inkjet printers.. One is a magnetic stirrer and the other overhead with polypropylene coated steel shaft.

The overhead one draws about 1 amp at twelve volts and will easily throw the contents out of a vessel if run too fast.

[Edited on 1-11-2006 by bio2]

Hilski - 1-11-2006 at 14:26

Sorry. Let me clarify that. I mean all the ones I have are stepper motors. I had 2 Epson printers, and all the motors out of both of those printers are stepper motors.
I'll look for an HP inkjet to tear apart at work. Maybe I'll get lucky.

Thanks.

-Hilski

YT2095 - 2-11-2006 at 01:54

you can buy cheap electric screwdrivers that will do the job quite nicely, I used one for a Ball Mill I made years ago, you only need the cheap plastic sorts that cost about 4 GBP.

gsd - 2-11-2006 at 09:44

Quote:
Originally posted by Hilski


I guess I'll just use the kitchen mixer for the time being until I get a more suitable


To the best of my observation, you can not run kitchen mixer motors on continuous basis. If You have to operate your O/H stirrer for very long durations, they are not suitable for the job.

gsd

Rosco Bodine - 2-11-2006 at 11:25

It is much easier to do this sort of thing on a much larger
scale . When you get to HVAC ball bearing PSC motors having a 1/2" shaft , then you can get a set screw mounted arbor which bears a 1/2"-20 thread and mount
on that a jacobs chuck having the same thread .....
chuck your stirring rod into the thing like a drill in a drill press , and vary the speed using an ordinary variac .

To get good low speed operation , you will have to
take out the wave washer which comes in the motor
and sets excessive preload force on the ball bearings ,
flatten it nearly flat with a hammer , and reinstall it .
A little machine oil on the bearing shields to thin the heavy grease packed in the bearings is also needed
to free up the rotation and reduce the parasitic friction
for stable low speed operation .

Using only a varaic , the speed control is pretty stable
up to the 75% or so of the synchronous speed of the motor where it is operating on its stall slope , and
there is an equilibrium possible between the voltage
input , and the load presented which causes the motor
to seek and hold a speed where work output balances
power input . I have confirmed this in many experiments developing a hefty drive for a magnetic stirrer . Precision made motors of 48Y ( 5 5/8" ) diameter
open construction and having end finned rotors and
higher grade ball bearings , not the cheap chinese bearings , work very well in this regard , motors of a
size in the range of 1/12 to 1/6 horsepower , and it
hurts nothing to take a motor rated at the higher output
and a higher voltage like 1/6 at 240 , and run it at half
that voltage as a variable speed stirrer drive .

The best motor I found for this so far is a Marathon X269
and operating it using a small variac across the 0-120 range , even though the motor is rated for 1/6 at 240 . It is very smooth .

[Edited on 2-11-2006 by Rosco Bodine]

Hilski - 5-11-2006 at 08:41

Just an update:

I ended up using (temporarily) a small shaded pole AC motor I had. I think it came out of an old ice cream maker. I'm using a plain old dimmer switch to control speed, and it actually works pretty well as long as there is at least some load on the motor. I made a small paddle out of a piece of HDPE, and bent the end of a glass rod into a sort of 'U' shape so that it would grip the paddle and not let it fall off. I'll post pictures of this thing as soon as I have some.

I also found a cordless drill motor that I didn't know I had. It's just the motor with no chuck, but I'm sure it could be more precisely controlled than the AC motor can.

In any case, the current setup will stir the hell out of the manganous alum mixture, which was really my goal in the first place. Easily made benzaldehyde is finally within reach.

**I almost forgot: Someone mentioned using an electric screwdriver for this application. That would definately be super easy to rig up. But, all the electric screwdrivers I have seen only turn about 200rpm. Isn't that much too slow to make an effective stirrer? I think I will buy one and try it out just for the hell of it, because I am curious as to how well it would work.


[Edited on 5-11-2006 by Hilski]

Rosco Bodine - 5-11-2006 at 11:09

Lightly loaded , a shaded pole motor will work okay ,
but it is the most minimal and least efficient of all
the choices of motors which will work , and has to be
carefully matched to the task in terms of the load .

Probably the ultimate stirrer drive would be a DC servo motor equipped with an encoder and an active speed
control .....but grab your wallet if you can't scrounge
such a motor for cheap , as the motor alone will cost
hundreds of dollars .

Some of the EMC appliance motors could possible be adaptable , but even they are fairly expensive .

One of the surplus old disk drive , or reel tape drive
servo motors from the early days of the computer industry , could also be adaptable ...and some of these
have encoders or a bare encoder shaft as a stub where
you can perhaps mount a small encoder wheel . Some
of these motors should have good speed control just
operating open loop and controlling the voltage .

And a last possibility you might look at is those motors
which are used for the radiator fans in automotive applications . For a light to medium duty requirement
these may be the cheapest and easiest solution .

[Edited on 5-11-2006 by Rosco Bodine]

stirrer chuck

Magpie - 15-11-2008 at 20:48

I recently aquired a Wheaton overhead stirrer. I plan to use it in round bottom flasks, etc, when magnetic stirring is not adequate. It is used and did not come with a chuck for securing the mixer shaft. For purchase of a chuck I have narrowed my options to two:

1. A 1/4" Jacobs Multi-Craft chuck and an "arbor attachment for an electric motor." Cost: ~$17

2. An Ace Glass nylon flexible chuck for 6mm shafts. Cost: ~$26. See picture below.

The Jacobs chuck would be more clunky but could take shaft diameters from about 1/16" up to "1/4" (6.4mm), and provide a very positive grip.

The Ace chuck looks to be very light and simple, and have the advantage of being somewhat flexible. It is limited to shafts at or very near 6mm diameter.

Does anyone have any experience with the Ace type chuck? Please let me know your experiences and recommendations.

[Edited on 15-11-2008 by Magpie]

chuck 8124.jpg - 3kB

S.C. Wack - 16-11-2008 at 00:53

It does what it is supposed to do but will spin a little unbalanced if something is not perfect when it is set up. If you pay Ace prices, you will be pissed when you get it because it cost less than a dollar to make.

Before this product and maybe still, real chemists used a tight-fitting piece of stiff rubber tubing between glass and metal shafts. A short piece of vinyl tubing wraps around the shaft here on the 8124.

An experience that you'll like is collecting the whole set. When the motor, chuck, a Trubore (neater than the bearings that are greased ground glass adapters), the rod and blade all come together as one piece inside your flask, it's a cool thing for the amateur. Don't know if you win if you end up with the most toys, but it's a good feeling having and using them.

EDIT: Well I can run the scanner using a sucky driver through Photoshop, just not as standalone app anymore thanks to Microsoft. So here is the instruction sheet - this shows the parts. The 10 mm version is 1 7/8" long and uses a 3/8" motor shaft. I'm not sure that Ace sells to individuals anymore BTW.

[Edited on 16-11-2008 by S.C. Wack]

Attachment: flexgrip.pdf (82kB)
This file has been downloaded 626 times

Magpie - 16-11-2008 at 12:32

Thanks S.C.

I have one further option in the works. I have asked VWR to quote me a price on a Wheaton chuck. But I'll be surprised if that doesn't come in north of $100. It looks like a very small Jacobs chuck w/shaft adapter.

The use of a piece of vacuum tubing sounds like it would definitely have merits: good flexibility, lightness, slip at excessive torque, and almost zero cost. I may just give this a try before investing in anything else.

starman - 18-11-2008 at 16:06

I've read over Roscoe's posts a few times and must admit most is going over my head.What are the general principles for a motor suited to "continuous operation."The little 12V dc motor I have in my mag stirrer/mantle seems to be about 10W (draws about 850mA @ 12V). I was thinking of purchasing something similar but higher wattage(around 35W or so) with a simple dimmer switch set up to build a light duty(not more than a litre flask) o/head stirrer.I'm thinking that this is probably similar to the radiator fan motor that Roscoe refers to.My worry here is possible sparks, overheating etc when used with volatile solvents.As a second question are the motors in a kitchen mixer any different than say a milkshake maker?At least with that you start out with a decent length shaft and mounting arrangements.I would have thought any of these AC appliance motors would burn out in farly short order?

kalacrow - 24-11-2008 at 11:36

Electric Fan Motors.

These are available in all sizes, all types, rated for DC or AC and can be had at junk shops for next to nothing.

Or you can buy a small electric fan and convert it. They are very cheap.

They even come with a convenient stub for mounting a flexible shaft.

You probably wouldn't want to stir anything too viscous, but for regular reactions I can't imagine them not being able to do the job. With an AC one, you could just use a light dimmer to control the speed.

Other possibilities for more torque (these are all BIG):

- Any wood saw motor, especially one from a table saw
- dishwashing machines
- tabletop grinders
- wheel chair motors.

for smaller ideas...

- Electric R/C car motors (also, look around for "robot wars" motors. These guys are very good at finding cheap alternatives)
- automotive power window motors
- automotive windshield wiper motors

These small ones are usually permanent magnet DC motors and easy to control. They don't normally put out too much RPM, but they do have good torque, so you could rig a gearing or belt system that gave you more RPM. Also, with a DC motor like this, you'll need a speed controller of some kind.

Here's a link that might help:

http://coolrobots.com/builders/newbie.html




-

starman - 25-11-2008 at 02:43

@kalacrow,thanks for the ideas.I have actually already built one a few years ago using an AC fan motor(they are after all made to run continuously)With the aid of some thread tape a 10mm drill chuck went on the shaft nicely.However without the fan attached the motor gets incredibly hot within half an hour,I wasn't game to run it longer than that and only ever used it on aqueous solutions.Additionally the torque isn't great.(can be stopped by hand).I will research the suggestions (particularly the automotive side) and hopefully see some more contributions to this thread.

S.C. Wack - 7-4-2010 at 07:32

For years I used a drill and paint stirrer when I could (sucks to rig, useless for flasks), and later got real lab stirrers and blades and glass shafts for use with real glassware. I still have to improvise some there because my stirrers go back to the 70's at least and one may be from the late 50's even, and these use 1/4" steel shafts, which are inconvenient for adapting to my 10 mm glass shafts. I've never seen a small electric stirrer using a 3/8" metal shaft at any of the auctions I go to.

I bought a paint stirrer at Lowes or somewhere a couple months ago that could be useful for anyone that uses a container that these will fit in for reactions, and has an old 1/4" stirrer: see at squirrelmixer.com. These have 1/4" steel (which can obviously be coated for use with acids) shafts, in the gallon/quart size. The 5 gallon size has a 5/16" shaft. This is still useless for flasks, and the shaft could be longer, but that's how it goes.

densest - 7-4-2010 at 19:24

For this sort of application you want a "gearmotor". Little electric motors want to go very fast - much too fast to be useful as stirrers. Little motors typically go 10000-30000 RPM. You want 30-600 RPM to stir things. Electronic surplus houses and robot suppliers and RC car suppliers sell various gearmotors for $US 3-10. They typically run from 2-24VDC, easily available from very cheap "wall wart" power supplies. I took one such from an old printer, a piece of heavy teflon tubing for a shaft, and made a crude paddle on the end. 5VDC was slow, 12VDC was medium, 24DC was fast. Total outlay was $0 since I already had a roll of Teflon tubing from EBay ($10 or so, a -real- bargain), old power supplies from dead computer gear, and the motor came from a printer I scrapped. The hardest part was making a "bearing" to run the shaft through a stopper for the flasks. A piece of HDPE made a slippery block to put the shaft through which didn't wear the soft teflon to shreds.

Cheap, worked fine, still have it & use it.
You could use a glass rod for a shaft, for instance, and mold a paddle onto the end.

Cloner - 1-5-2010 at 02:22

A quick and dirty way to build a stirrer is to use a ventilator and tube. You remove the fan and put a few cm of tough rubber tube (propane burner tube does the job, or vacuum tube) on the rotating bar. On the other side of the tube you put the stirring bit which can be a wooden kitchen spoon or whatever is inert to your reaction mixture. Rubber tube can transmit rotation in angles but don't expect it to last if the angle is too great.

chief - 1-5-2010 at 04:26

A drilling engine at reduced voltage will run slowly ... and more silent ...

peach - 1-5-2010 at 06:39

Yeah, I agree with the others, you'd be better going with something featuring gears.

A microwave turntable motor is remarkably strong, but it does have a fairly low RPM.

Be extremely careful with your solvents, things like cheapo electric whisks can put out some serious sparks from the brushes.

For the coupling, you can buy plastics that melt at 60C and thermofom. You could easily use some of that to custom build a chuck for just about anything.

As for the bearing, just buy a rubber stopper and drill out the center to roughly fit the rod. Line it with some grease to smooth things out.

If you don't need it to be gas tight, which will be difficult to achieve with just about every home made option, then having a tiny amount of freedom in the position of the rod may actually help it deal with bumps.

On the subject of PTFE collars, this gimp once purchase around $200 worth of them to fit specialized glassware, only to have said glassware perish at a later date.... ho hum...